The load in such drawworks is routinely fastened to a flexible traction element which is usually formed as a steel cable. For the purpose of lowering and hoisting, the winding drum is rotatably driven so that the flexible traction means is unwound or wound up.
In the case of drawworks according to the prior art, as are described, for example, in WO 03/072904 A1, the winding drum is fastened in a rotationally fixed manner to a winding shaft whose axis extends approximately parallel to the longitudinal sides of the frame. The winding shaft is mounted in bearing blocks which are fixedly connected to the frame beyond the two end sides of the winding drum. As seen from the winding drum, a braking device acting on the winding shaft is provided beyond one bearing block. It is routinely designed as a disk brake device and comprises a brake disk, which is connected to the winding shaft in a rotationally fixed manner, and brake caliper arrangements fastened to the frame. The brake disk can also be arranged directly on the flanged drum disk.
As seen from the winding drum, there is provided, beyond the other bearing block, a gear unit which, in the case of the exemplary embodiment described in WO 03/072904 A1, comprises two individual gearboxes and a summing gear connected to the winding shaft. The gearboxes are fixedly connected to the frame. The housing of the summing gear is connected to the frame via a torque support.
In order to avoid a situation in which distortions of the frame (which are unavoidable if, for example, the underlying surface on which the frame is mounted subsides, or which can occur during temperature changes) result in stresses in the winding shaft and the gear arrangement which increase wear or even damage the entire drawworks, the gearboxes are connected to the summing gear via flexible couplings.
In another drawworks, the summing gear is likewise fixedly connected to the frame. A flexible coupling is then provided between the output shaft of the summing gear and the winding shaft.
Although, on account of the flexible couplings, certain distortions of the frame can be compensated for, care must be taken in the case of these drawworks to ensure that the frame is precisely oriented on the underlying surface to provide an alignment or parallel-running of all the axes and shafts of the drawworks since the couplings permit only limited deviations from the parallel or aligned orientations of the axes or shafts and the loading of the couplings increases as the deviations increase. The frame must therefore be designed to be as distortion-resistant as possible, which unadvantageously increases both its weight and its manufacturing costs. Experience has moreover shown that the frame must be routinely realigned in the course of the operation of a drawworks since the underlying surface subsides on account of the dynamic load changes which act on the drawworks during the lifting and lowering of loads.